help with tables

[#1]

dt = current data table();
dt << subset(by(:p20000), All Rows, All Columns);

//When I subset dt by :p20000, it outputs atmost 3 data tables ‘p20000=1000’, ‘p20000=1001’, ‘p20000=1002’.
//What I do next is to check if such dt exists 

exist= Try(Data Table("P20000=1002");tableExist = 1,tableExist = 0);

);

//if tab_1002,
tab_1002=expr(insery my long script here);
//if tab_1001,
tab_1001=expr(insert script here);

So if p20000=1002 exists, I will use the expression tab_1002,
and if p2000=1001 exists, I will use the expression tab_1001.

However there are some cases where when subsetting, only data table p20000=1000 exists.

Im confused how to do these with conditions.

[#2]

You may be able to use this kind of approach:

NamesDefaultToHere(1);

dt = Open("$SAMPLE_DATA/Big Class.jmp");
dtList = dt << subset(by(:sex), All Rows, All Columns);
for(t=1, t<=NItems(dtList), t++, Print(dtList[t] << getName));